This invention relates to an additive for high solids coating compositions that improves appearance of a finish of the compositions.
High solids coating compositions containing a relatively low molecular weight acrylic polymer and an alkylated melamine crosslinking resin are known in the art as shown by Thompson et al. U.S. Pat. No. 4,330,458 issued May 18, 1982 and Khanna et al. U.S. Pat. No.4,276,212 issued June 30, 1981. These compositions require a strong acid catalyst to catalyze the crosslinking reaction and provide adequate cure at typical baking temperatures of about 125.degree. C. To provide a stable coating composition, an amine is added to neutralize the acid. After application of the coating composition to a substrate, the composition is baked and during baking the amine is released to unblock the acid to catalyze the reaction. Many conventional amines cause problems such as poor stability of the composition during storage, inhibition of cure during baking or cause the finish to have a poor appearance resulting from a differential rate of curing which causes macrowrinkling and low gloss. These coating compositions often have other problems such as sagging of the finish on application and improper orientation of metallic flake pigments which cause a poor appearance.
There is a great need for an additive for high solids coating compositions that will neutralize the acid and provide a storage stable compositions, that will unblock during baking and allow the acid to catalyze the crosslinking reaction and cure the finish, reducing sagging of the finish on application and provide for proper orientation of metallic flakes used in the coating to enhance the appearance of the finish. High solids coating compositions containing such an additive will be acceptable for use in coating automobiles and trucks.